Two pole, insulated magnets are well known in the art, typically utilizing ferrite ceramic magnet material. Ceramic magnets of the fixed ferrite type have come into widespread usage within the past 50 years due to their excellent magnetic properties. Ceramic ferrite magnets are electrically non-conductive, hard, and much lighter in weight than magnets made of metallic alloys. They are also very resistant to demagnetization, and evidence very low eddy current losses. They are permanent magnets which have a very high coercive force values and high maximum energy products. Because of these properties, ceramic ferrite magnets are often incorporated into structures which require a large magnetic area but a relatively short magnetic length.
In the prior art method, a ceramic magnet is sandwiched between two ferrous poles. The sandwich assembly is then placed in a brass or aluminum cup such that the ends of the poles protrude beyond the edge of the cup. The cup is then filled with an epoxy or liquified plastic, which is allowed to harden, resulting in a finished magnet assembly.
Although such magnets are in widely available usage, the product does have its limitations, both in terms of production and of usage. In particular, the epoxy potting material and the brass or aluminum cup are not particularly amenable to machining, thus limiting the usefulness of the assembly.
In addition, the prior art process of manufacture is time consuming, requiring a cure cycle for the epoxy or liquified plastic; it may take as long as 15 minutes for the plastic or epoxy to cure so that the completed product can be handled, stored and moved. In addition, there are potential alignment problems when these products are manufactured by the prior art methods. In particular, it is difficult to ensure that the opposed magnetic pole pieces are correctly oriented in relation to the cup.
Despite the obvious disadvantages noted above, the prior art process of forming the magnetic assembly by encapsulating the magnetic sandwich in epoxy potting material is, so far as is known, virtually universally used in the industry at the present time.
Clearly, it would be desirable to have a two pole, insulated ceramic magnet assembly which does not include the brass sleeve and epoxy potting material of the prior art and is, thus, more amenable to machining and other shaping processes.
It would also be desirable to produce such a magnet by a method which is less time consuming, does not require a lengthy curing step, and which ensures that the magnetic pole pieces are in correct alignment with respect to the remaining elements of the magnetic assembly.